Ever since the invention of radio communication by Marconi in 1897 there has been an effort to reduce the size of antennas and radio equipment. The early broadcast radio receivers employed bulky tuners and vacuum tubes, and required external long-wire antennas. Later miniature vacuum tubes were developed permitting portable radio receivers, and it was discovered that a flat pancake coil mounted to the rear panel of the radio receiver could provide an unobstrusive AM antenna. The power cord of the radio was typically used as an FM antenna.
With the introduction of the transistor in the 1950s, pocket-size radios were economical to mass produce. For the AM broadcast band, a coil antenna was wound on a ferrite core to further reduce its size without excessive loss of signal. For the FM broadcast band, a telescoping whip antenna was used, preferably extensible to a quarter wavelength.
Today integrated circuitry permits the manufacture of miniature pocket pagers, "wrist" radios, and radios fitting into light weight stereo headphones. The shrinking of the antenna to accommodate the smaller radios does, however, severely reduce the received signal levels. The antennas for these miniature radios typically consist of internal tuned coils connected to belt buckles, wrist straps, or dangling wires.